Scott Doak did a GREAT job of putting this information together. With
his permission, I have kept the information in tact as a reference for
those who want a good introduction to genetics in general, and specific
to Quakers and other avian species. Thanks Scott.
Introduction:
We don't claim ownership or originality for the genetics information
which follows. It is the product of significant non-avian genetics
knowledge coupled with considerable input from folks on the
"Genetics-Psittacine" list. An attempt has been made to simplify much
of the scientific lingo and produce an accurate and understandable
description of Quaker genetics for the average reader. We have found
the online Quaker community to be free with "inside" information to us
as we started our breeding program, and hope this can be of some help to
those without a depth of genetics understanding. We welcome any and
all feedback which may help these pages become more accurate and
informative. Please drop us an email if you have any suggestions.
For those of you well versed in the basics of avian genetics, feel free
to jump right to the more in-depth autosomal and sex-linked discussions.
If you're a pro with genetic notation, go right to the genetics tables
where you can predict the genetic make-up of offspring for any of the
54 possible parental combinations of the green, blue, and pallid traits.
With these tables you can predict the inheritance of the Blue, Pallid
(Dark-Eyed Cinnamon), Cinnamon (Red-Eyed Cinnamon), and Lutino traits as
well as almost any combination thereof. The inheritance patterns of
the emerging Yellow and Pied mutations are less understood at this
point. For those of you in need of a quick avian genetics refresher
course, read on.
Color:
To understand the inheritance of genetic color mutations, one must first
understand the basics of why colors occur. In most parrots, including
Quakers, there are 2 pigments at work. The first is a yellow pigment
called psittacin. (sit'-uh-sin) It appears yellow because it primarily
reflects yellow light to our eyes. The second is a black pigment called
melanin which is also the sole pigment which occurs in humans. This
pigment appears black or gray in areas without feathers such as eyes,
legs and toe nails. However, the melanin in the feathers of a Quaker
appears as a dark blue because the structure of the feathers bends and
scatters the light in such a way that we see predominately dark blue
light reflected. The upshot of this is that both yellow and dark blue
light are visible reflecting from Quaker feathers. The combination of
these two colors in the feathers is seen as dark green. (dark blue +
yellow = dark green) The combination of these pigments and colors are
graphically depicted below.
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Yellow Color
Intact
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+
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Dark Blue Color
Intact
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=
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Green Quaker
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It then follows that if the yellow pigment (psittacin) is suppressed by a
genetic mutation, you would get a dark blue Quaker. This is what we
call a "Blue" Quaker.
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Yellow Color
Suppressed
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+
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Dark Blue Color
Intact
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=
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Blue Quaker
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If the blue pigment (melanin) was suppressed, you would expect a yellow
Quaker. This is what is happening in the Lutino Quaker.
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Yellow Color
Intact
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+
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Dark Blue Color
Suppressed
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=
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Lutino Quaker
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So, it is easily seen that Blue Quakers and Lutino Quakers are exactly
the opposite of each other. Each has one of the pigments (melanin and
psittacin) completely intact and one completely suppressed. One just
has the opposite pigment from the other.
The difference between a Pallid (Dark-Eyed Cinnamon) and a Cinnamon
(Red-Eyed Cinnamon) and their mutations' effects on pigment are a bit
more complex. But, they both have to do with the fact that the black
melanin pigment (seen as dark blue) is altered in appearance or
quantity.
The best supposition of experienced mutation breeders currently is that
the Pallid (Dark-Eyed Cinnamon) Quaker has a partial reduction in the
amount of black melanin (seen as dark blue) pigment. So, instead of a
dark blue contribution from the melanin, only a light blue is present.
This results in the overall color of the Pallid Quaker being a lighter
green or more pallid appearing bird. Hence, the name "Pallid" is
appropriate.
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Yellow Color
Intact
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+
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Dark Blue Color
Partially Intact
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=
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Pallid Quaker
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The case of the Cinnamon (Red Eyed Cinnamon) Quaker is somewhat
different. Just as in Cinnamon mutations of other species, the amount
of melanin pigment is roughly the same. However, one of the steps that
converts the initially synthesized brown melanin to black melanin is
blocked. Since brown melanin is not as dark as black melanin, the blue
color seen is lighter and similar to that of the Pallid (Dark Eyed
Cinnamon) Quaker but carries a slightly brownish tone. When this light
brownish blue is added to the yellow, a cinnamon color results.
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Yellow Color
Intact
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+
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Dark Blue Color
Lightened & Brownish
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=
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Cinnamon Quaker
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What we call a "Pallid Blue" is simply the result of the combination of
the "blue" and "pallid" Quaker traits as shown in the examples above.
The yellow pigment is suppressed as with the Blue Quaker example AND the
dark blue (melanin) pigment is partially suppressed to a light blue as
in the Pallid example. The result is that only a light blue color is
seen in the Pallid Blue as depicted below.
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Yellow Color
Suppressed
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+
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Dark Blue Color
Partially Intact
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=
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Pallid Blue Quaker
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What we call a "Cinnamon Blue" is simply the result of the combination
of the "blue" and "cinnamon" Quaker traits as shown in the examples
above. The yellow pigment is suppressed as with the Blue Quaker example
AND the dark blue (melanin) pigment is lightened with a brownish tone
as in the Cinnamon example. The result is that only a light brownish
blue color is seen in the Cinnamon Blue as depicted below.
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Yellow Color
Suppressed
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+
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Dark Blue Color
Lightened & Brownish
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=
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Cinnamon Blue Quaker
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And, finally, if we combine the "Blue" and "Yellow" Quaker mutation
traits in the 2nd and 3rd examples, a "White" Quaker would be expected.
This is illustrated below.
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Yellow Color
Suppressed
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+
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Dark Blue Color
Suppressed
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=
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Albino Quaker
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Keep in mind that this is an oversimplification of how things really
work. Specifically, melanin (which produces the blue color) is
partially or completely suppressed in many different ways. It can
remain intact in the eyes, legs and feet in Dark-Eyed Yellow (Yellow),
Dark-Eyed Cinnamon (Pallid) or Dark-Eyed White (White) types or it can
be suppressed in these areas in their Red-Eyed Yellow (Lutino), Red-Eyed
Cinnamon and Red-Eyed White (Albino) counterparts. There are many
other factors involved which affect various areas of the plumage
differently and there are many other potential mutations (judging by
other psittacines such as Ringnecks) that will emerge and complicate
this picture. However, it gives a beginner a starting point.
The Wildtype Concept:
Before getting into genetics and the notation involved, it is imperative
that one understand the concept of a wildtype bird. Simply put, the
wildtype bird is the one we are used to seeing in the wild. For the
Quaker, this is a medium to dark green bird with a few dark blue flights
and tail feathers and gray on the chest, cheeks and forehead. We also
expect this "normal" Quaker to have black eyes and nails, gray legs and
feet and a pinkish bill. Subspecies aside, virtually all wild Quakers
fit these basic criteria. These "wildtype" traits are the backdrop
against which we will base the following genetic mutation discussion.
The key to the wildtype concept is this: Any time a particular mutation
being discussed is absent, it is assumed that the "normal" or "default"
or "wildtype" appearance is present.
Basic Genetics:
Inside the nucleus of every cell in any animals body lies several pair
of chromosomes. In humans, there are 23 and in birds there are usually 6
to 10 pairs (depending on the species) as well as a number of
"microsomes" which will be ignored in this discussion. One pair of
these chromosomes are "sex" chromosomes which we'll deal with later.
Chromosomes are made up of genes linked end to end. It is the gene that
is the base unit for genetics. Each gene has a specific place on a
given chromosome and is responsible for a specific trait such as eye
color in humans or yellow pigment in Quakers. In humans, part of one
chromosome may look like this.
Each chromosome contains literally millions of genes which code for
everything from simple traits such as eye color in humans to
personality, size and fertility in Quakers. The important issue to keep
in mind, though, is that each gene has two copies; one on each
chromosome in the pair. If these two copies both contain the same trait
(such as light colored eyes in a human or the lack of yellow pigment in
a Quaker) then there is no problem and the trait is expressed (meaning
seen externally) as a light-eyed human or a Blue Quaker. (since it lacks
yellow pigment)
Dominant and Recessive Traits:
True genetics come into play when the two copies of the gene have
different information such as one coding for light colored eyes and one
coding for brown eyes. (whether the light eyes end up being green, blue
or hazel is a bit more complicated) In cases like this, one needs to
know which (if either) of the genes "wins" the conflict. We term the
"winner" the dominant gene and the "loser" the recessive gene. In the
above case, brown eyes are dominant and light eyes are recessive in
humans. So, if someone had one copy of each gene, they would have brown
eyes expressed. (seen externally) They would look exactly like someone
who had two copies of the brown eyed gene, but would be genetically
different.
Genetic Symbols:
When discussing a single and simple trait, such as eye color in humans,
it is possible to describe in text what is happening genetically such
that it is easily understood by a reader or fellow breeder. However,
when numerous traits and/or sex-linked traits are considered, it becomes
confusing in a hurry. This is why genetic notation (or short hand) was
devised. It is a way to describe complex genetic traits using symbols
and makes even the most complicated combination of traits not only easy
to follow, but easy to predict as well.
Each mutation occurs at a specific gene. (or site) A "light-eyed" human
is a result of a mutation at the human "light-eyed" gene (AKA
"light-eyed" site) while the "Blue" Quaker is the result of a mutation
at the Quaker "blue" gene. (AKA "blue" site) The letter "L" is chosen
to describe the pair of genes at the "light-eyed" site in humans and the
letter "B" is chosen to describe the pair of genes at the "blue" site
in Quakers. Either a "L" or "l" can be used at the "light-eyed" site in
humans and either a "B" or "b" can be used at the blue site in Quakers.
The "L" represents the dominant gene and trait for eye color in humans
(in this case brown) and the "l" represents the recessive gene and
trait. (in this case light-eyes) The "B" represents the dominant gene
and trait for feather color in Quakers (in this case green) and the "b"
represents the recessive gene and trait. (in this case blue)
To review . . .
L = brown-eyed gene in humans
l = light-eyed gene in humans
B = green gene in Quakers
b = blue gene in Quakers
Any time you see a capital letter or letters, the trait is dominant and
any time you see a lower case letter or letters, the trait is recessive.
So, knowing nothing else about the trait, you can predict it's
inheritance just by looking at the genetic notation. All of the
mutations on this site are recessive, so whenever you see a symbol
capitalized, you know it is the 'wildtype' gene and trait and whenever
you see a symbol in small case, you know it is the mutated trait.
(B = wildtype "green", b = blue, P = wildtype "green", p = pallid)
However, there are mutations in other psittacines that display dominant
characteristics and it is expected that these will eventually be found
in Quakers as well. (an example is a "dark factor" mutation designated
by "D" or "d") Since the mutation is dominant and the capitalization of
the symbol means it's dominant, "D" represents the mutation and "d"
represents the 'wildtype'. As this would mess our tidy "all symbols
with caps are the mutated genes" rule, a clarification is needed. This
clarification is adding a superscript "+" to any symbol that represents a
'wildtype' characteristic.
To review further . . .
L+ = wildtype "brown-eyed" gene in humans
l = light-eyed gene in humans
B+ = wildtype "green" gene in Quakers
b = blue gene in Quakers
D = dark factor gene in Quakers
d+ = wildtype "green" gene in Quakers
Another way to think of this is to assume a trait we'll call "test"
using the "T" as the designated letter for it's gene. Without knowing
anything about the trait, you can predict quite a bit just by seeing
what notation is used in the following examples:
T+ = dominant wildtype gene/trait
t = recessive mutated gene/trait
T = dominant mutated gene/trait
t+ = recessive wildtype gene/trait
So, by viewing genetic symbols, several conclusions can be drawn. All
capitalized symbols are dominant genes/traits, all small case symbols
are recessive genes/traits, all symbols followed with a superscript "+"
are 'wildtype' genes/traits, and all symbols without a superscript "+"
are mutated genes/traits.
Understanding what the symbols mean, we can now place them together in
pairs Here is an example of the possible combinations at the human
"light-eyed" site with aviculture lingo in parentheses.
L+ L+ = Brown-eyed person with 2 copies of the brown-eyed gene
(visual brown-eyed human)
(brown-eyed)
L+ l = Brown-eyed person with 1 copy of the brown-eyed gene
and 1 copy of the light-eyed gene
(visual brown-eyed human split for light-eyed)
(brown-eyed/light-eyed)
l l = Light-eyed person with 2 copies of the light-eyed gene
(visual light-eyed human)
(light-eyed)
If we take this example to our beloved Quakers, it is no different.
These are the possible combinations at the Quaker "blue" site with
aviculture lingo in parentheses.
B+ B+ = Green Quaker with 2 copies of the green gene
(visual Green Quaker)
(Green)
B+ b = Green Quaker with 1 copy of the green gene
and 1 copy of the blue gene
(visual Green Quaker split for Blue)
(Green/Blue)
b b = Blue Quaker with 2 copies of the blue gene
(visual Blue Quaker)
(Blue)
As you can see from the above two examples, any recessive trait must
exist with two copies or it won't be expressed visually. Conversely, a
dominant trait only needs a single copy of a gene to be expressed.
There are several other genetic relationships aside from simple dominant
and recessive such as "co-dominance" and "variable penetrance" that are
not addressed in the following pages. These and others are found in
other species, but have yet to find their way into Quaker genetics as
we're still in the early phases of discovering and categorizing color
mutations.
By now you should . . .
- understand why color occurs in Quakers and the pigments involved.
- know how the known color mutations are manifested in Quakers.
- understand what pairs of chromosomes and genes are and what's so important about the fact they come in pairs.
- know the concepts of dominant and recessive traits.
- be able to determine the visual color of a Quaker just by seeing
the genetic notation and knowing what mutation is being considered.
(B+B+, B+b, bb)
If these concepts are not clear at this point, you may want to review this page again before going on.
Had enough? Go back to our Home Page and surf some other stuff.
Thirsty for more? Continue the tutorial at the Autosomal Traits page.
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